Conventional color photographic systems use an optical system to project a focused image onto a film having multiple light-sensitive layers. These multilayer color films have several disadvantages when compared to black and white (B/W) film emulsions. Processing of silver halide (AgX) in color film is a slow process because development chemistries must diffuse through a thicker depth of emulsion than found in black and white film emulsion. Lower layers of film emulsion lose speed because of light loss due to silver halide particles in the upper layers. Also, light traveling through the thick, multilayer film loses sharpness through light scatter. These multilayer color films store the image as formed dyes which are not as permanent as the silver metal in black and white film images. Finally, the complexity and therefore the cost of color multilayer films is greater. It would be advantageous to use a black and white film emulsion to make color images.
Recent advances in optical microstructures have allowed the creation of high resolution (10 micron) color filter arrays (CFA). The resolution of these CFA's is high enough to match the resolution required for simple consumer imaging. These arrays are used on CCD imagers to filter the panchromatic (sensitive to all visible wavelengths) to separable colors. Multiple structures have been proposed for these CFA's. It is preferable that the CFA filter out ("throw away") only a small fraction of the light passing through the filter to transfer therethrough the greatest light signal possible. It is also advantageous to store high resolution luminance (panchromatic) data and lower resolution color data for the image. In both color television and Photo CD systems, efficient use of image structures is achieved by recording high resolution panchromatic (composite red-green-blue {RGB}) signals and two lower resolution color recordings.
The Polachrome Instant Slides process prints a CFA treated light signal onto a black and white reversal film emulsion. Therein, the CFA consists of a series of red, green, and blue stripes on the film. An image is exposed on the film through the filter and developed into a slide. The earliest use of a color image silver halide emulsion system was by Joly (@ Dublin University, late 1800's).
Joly used a separate glass plate as the filter carrier. Later, the CFA and emulsion were united in the Paget process which was in use until the 1950's. The Paget process is unique in that a matrix of red, green, and blue pixels is used as the OFA on the film. All these systems have to provide optical-only displayable images. These systems suffer speed loss because each filter absorbs 2/3 of neutral (RGB) light. The present invention assumes that the film will be scanned, eliminating the need for optical projection, and allowing improved CFA structure.